Nuclear Genomic Sequences Reveal that Polar Bears Are an Old and Distinct Bear Lineage

• Published in: Science
• Main Authors: Hailer, Frank, Kutschera, Verena E., Hallström, Björn M., Klassert, Denise, Fain, Steven R., Leonard, Jennifer A., Arnason, Ulfur, Janke, Axel
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Association for the Advancement of Science (AAAS) 2012
• Subjects: Arctic; brown bear
• Online Access: http://dx.doi.org/10.1126/science.1216424; https://www.science.org/doi/pdf/10.1126/science.1216424

Ancient Bears Polar bears are well known for adapting to their cold Arctic climate. Some recent studies, based on mitochondrial DNA, concluded that they are a relatively young species and that these adaptations occurred quite quickly. Although mitochondrial DNA is regularly used to estimate evolutionary history, it has some well-known drawbacks, including sex-biased dispersal and hybridization. Thus, Hailer et al. (p. 344 ) looked at neutral genetic data that are distributed more widely across the genome of a relatively large sample of polar, brown, and black bears. Consistent with fossil-based studies, the analysis reveals polar bears as a sister lineage to all brown bears, with an estimated divergence time of 300,000 to 900,000 years ago. Thus, polar bears are indeed of a more ancient lineage, and more recent estimates based on mitochondrial DNA are likely to have been affected by past hybridization with brown bear.